To get the messages from that board to not appear just in that component would unfortunately require a customization.  The customization typically involves creating a custom setting to exclude the board from the landing page activity feed, and then in the activity feed component we have to add logic to get a list of boards that DON'T have that setting set, and get the messages from those.  At the very least adding the custom setting would likely require a Professional Services engagement to create the setting and make it available in the API.  ... View more

As of 22.3 the API (which is used for that activity feed) will now respect the admin setting "hide messages in this board from lists". Admin > Community Structure > (Hover over a board) > Edit Properties This will keep the messages from that board from appearing in message lists outside that board (unless explicitly queried for). They will still appear in places like the search. ... View more

Hiding ("Hide from lists and menus" setting) a board or category, does only that: hides it from showing up in OOB lists and menus. It does not prevent someone from getting to it via direct link, or it appearing in API results, and obviously, from RSS feeds. If you do not want the board to be publicly accessible, you have to restrict it using permissions. ... View more

Without authentication, you'll only be able to get public content. So if that message UID is in a private area that would otherwise require authentication, you won't be able to get it from the API without authentication. ... View more